Sum of the Measures of the Angles in a Triangle

Move the slider to adjust the measure of the green angle. You can also change the measure of the red angle by moving the vertex. Answer the questions below.

1. Position the slider on 90°. What kind of triangle is this? Record the measures of the three angles and calculate the sum.
2. Now move the slider to 40°. How can we classify this triangle? Record the measures of the angles and calculate the sum.
3. Finally, move the slider to 130°. What do we call this kind of triangle? Record the angle measures and calculate the sum.
4. You have now calculated the sum of the angles in three different kinds of triangles. What do you suppose will be the sum of the angles in any triangle you create?
5. Move the slider to two more values and check your conjecture. Were you correct?
6. If we had a new student come to class tomorrow, how would you explain what you learned today?
7. Go to this website and practice what you learned until you get five problems correct: http://www.geogebratube.org/student/m94320